Method and device for clock synchronisation with a vestigial-sideband-modulated transmitted signal

Abstract

A method for clock synchronisation between an amplitude-modulated or phase-modulated received signal (r(t)) and a transmitted signal (s(t)) estimates the timing offset (ε) between the received signal (r(t)) and the transmitted signal (s(t)) by means of a maximum-likelihood method. The maximum-likelihood method in this context is realised by an estimation filtering (S 40 ; S 140 ) dependent upon the transmission characteristic, a subsequent nonlinear signal-processing function (S 50 ; S 150 ) and an averaging filtering (S 60 , S 100 ; S 180 , S 200 ). The received signal (r(t)) is especially a modified vestigial-sideband-modulated received signal (r VSB ′(t)). The nonlinear signal-processing function (S 50 ; S 150 ) maintains the alternating component in the spectrum of the pre-filtered vestigial-sideband-modulated received signal (v VSB ′(t)).

1. A method comprising:
 estimating a timing offset between a received signal and a transmitted signal using maximum-likelihood estimation, wherein the step of estimating includes, 
 performing estimation filtering on the received signal dependent upon a transmission characteristic to obtain a filtered signal, 
 utilizing a nonlinear signal-processing function on the filtered signal to obtain a nonlinear signal-processed signal, and 
 providing an averaging filtering on the nonlinear signal-processed signal, 
 wherein the received signal is a modified vestigial-sideband-modulated signal and the nonlinear signal-processing function maintains alternating components in a spectrum of a filtered vestigial-sideband-modulated signal. 
 
   
   
     2. A method according to  claim 1 , wherein the modified vestigial-sideband-modulated signal is obtained by down mixing a vestigial-sideband-modulated signal by one quarter of a symbol frequency of the vestigial-sideband-modulated signal. 
   
   
     3. A method according to  claim 1 , wherein a symbol duration of the modified vestigial-sideband-modulated signal is half of a symbol duration of the signal. 
   
   
     4. A method according to  claim 1 , wherein the nonlinear signal-processing function is a squaring without modulus formation. 
   
   
     5. A method according to  claim 4 , wherein the squaring without modulus formation superimposes a squared real and imaginary component of the filtered vestigial-sideband-modulated signal having maintained the alternating components in the spectrum of the filtered vestigial-sideband-modulated signal. 
   
   
     6. A method according to  claim 1 , wherein a Fourier transform of a pre-filtered and squared vestigial-sideband-modulated signal is determined respectively at positive and negative symbol frequencies. 
   
   
     7. A method according to  claim 6 , further comprising:
 conjugating, at the positive symbol frequency, the Fourier transform of the pre-filtered and squared vestigial-sideband-modulated signal; and 
 multiplying a result of the conjugating by the Fourier transform of the pre-filtered and squared vestigial-sideband-modulated signal at the negative symbol frequency. 
 
   
   
     8. A method according to  claim 1 , wherein the averaging filtering includes a first averaging filtering and a second averaging filtering. 
   
   
     9. A method according to  claim 8 , wherein a bandwidth of the first averaging filtering is increased until spectral lines of the filtered and squared vestigial-sideband-modulated signal displaced respectively by a frequency offset of a carrier frequency relative to the positive and negative symbol frequencies, are disposed within a throughput range of the first averaging filtering. 
   
   
     10. A method according to  claim 8 , wherein the first averaging filtering is implemented before determining two Fourier transforms of a pre-filtered and squared vestigial-sideband-modulated signal taken respectively at a positive symbol frequency and at a negative symbol frequency. 
   
   
     11. A method according to  claim 8 , wherein the first averaging filtering is implemented after determining two Fourier transforms of a pre-filtered and squared vestigial-sideband-modulated signal respectively taken at a positive symbol frequency and at a negative symbol frequency. 
   
   
     12. A method according to  claim 9 , wherein a duration of an impulse response of the second averaging filtering is increased, until a duration of an impulse response of the first averaging filtering, reduced by the increased bandwidth, in combination with the duration of the impulse response of the second averaging filtering, reaches a total duration for smoothing interference superimposed on the pre-filtered and squared vestigial-sideband-modulated signal. 
   
   
     13. A method according to  claim 7 , wherein the averaging filtering includes a first averaging filtering and a second averaging filtering, and the second averaging filtering is implemented after multiplying the result. 
   
   
     14. A method according to  claim 2 , wherein in cases of an inverted position of a sideband of the vestigial-sideband-modulated signal, a mirroring of the sideband from the inverted position to a non-inverted position is implemented before down mixing the vestigial-sideband-modulated signal. 
   
   
     15. A method according to  claim 2 , wherein the vestigial-sideband-modulated signal is a vestigial-sideband-modulated signal including two real symbols, four real symbols, eight real symbols, 16 real symbols or M real symbols, wherein M is a positive integer. 
   
   
     16. An apparatus comprising:
 an estimator configured to estimate a timing offset between a received signal and a transmitted signal using a maximum-likelihood estimation, wherein the estimator includes, 
 an estimation filter configured to perform an estimation filtering on the received signal dependent upon a transmission characteristic, 
 a nonlinear signal-processing unit operatively connected to an output of the estimation filter, and 
 an averaging filter operatively connected to an output of the nonlinear signal-processing unit, 
 wherein the received signal is a modified vestigial-sideband-modulated signal and the nonlinear signal-processing unit is a squaring unit without a modulus former. 
 
   
   
     17. An apparatus according to  claim 16 , further comprising:
 a down mixer; and 
 a subsequent sampling and holding element, 
 wherein the down mixer and the subsequent sampling and holding element are connected upstream of the estimation filter, and 
 wherein the down mixer and the subsequent sampling and holding element are configured to generate the modified vestigial-sideband-modulated signal from a vestigial-sideband-modulated signal. 
 
   
   
     18. An apparatus according to  claim 16 , wherein the averaging filter includes a first averaging filter and a second averaging filter connected downstream of the estimation filter. 
   
   
     19. An apparatus according to  claim 18 , further comprising:
 a first discrete Fourier transformer; and 
 a second discrete Fourier transformer, 
 wherein the first and second discrete Fourier transformers are respectively connected between the squaring unit and the second averaging filter, and 
 wherein the first and second discrete Fourier transformers are configured to implement Fourier transformations at a positive symbol frequency and at a negative symbol frequency, respectively. 
 
   
   
     20. An apparatus according to  claim 19 , further comprising:
 a conjugator configured to conjugate Fourier transformations at positive symbol frequencies, 
 wherein the conjugator is either connected upstream or downstream of the first discrete Fourier transformer. 
 
   
   
     21. An apparatus according to  claim 19 , wherein the first averaging filter is connected upstream of the first discrete Fourier transformer and the second discrete Fourier transformer. 
   
   
     22. An apparatus according to  claim 19 , wherein the first averaging filter is connected downstream of the first discrete Fourier transformer and the second discrete Fourier transformer, respectively. 
   
   
     23. An apparatus according to  claim 21 , further comprising:
 a multiplier connected downstream of the first discrete Fourier transformer and the second discrete Fourier transformer or connected downstream of the first averaging filter and the second averaging filter, 
 wherein the multiplier is configured to multiply a conjugated Fourier transform of a pre-filtered and squared vestigial-sideband-modulated signal, and 
 wherein the conjugated Fourier transform is taken at a positive symbol frequency of a Fourier transform of the pre-filtered and squared vestigial-sideband-modulated signal taken at a negative symbol frequency. 
 
   
   
     24. An apparatus according to  claim 17 , further comprising:
 a unit configured for sideband mirroring connected upstream of the down mixer. 
 
   
   
     25. A digital storage medium including one or more electronically-readable instructions for causing one or more processors coupled to the digital storage medium to carry out the method of  claim 1 . 
   
   
     26. A computer readable medium including a computer program, wherein the computer program embodies code for implementing the method of  claim 1  on a computer or by a processor.